Gingival Changes in Wistar Rats after Oral Treatment with 4-Nitroquinoline 1-Oxide

OBJECTIVES 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue carcinogenesis is a useful model for studying oral squamous cell carcinoma. However, gingival changes following 4NQO administration via drinking water are absent in the literature. The aim of this study was to investigate gingival changes concomitant to tongue carcinogenesis induced by 4NQO by means of morphological analysis. METHODS Male Wistar rats were distributed into 3 groups of 10 animals each and treated with 50 ppm 4NQO solution by drinking water for 4, 12 or 20 weeks. Thirty animals were used as negative control. RESULTS Regarding tongue mucosa, the primary histopathological change i.e., hyperplasia and dysplasia was evidenced after 12 weeks treatment with 4NQO. At 20 weeks, squamous cell carcinoma was found in the majority of animals. Gingival squamous hyperplasia was induced by 4NQO after 20-weeks of treatment. Dysplastic changes appeared in some animals (two cases) as well. CONCLUSIONS Taken together, our results support the notion that 4NQO is more effective in rat tongue mucosa than gingival tissue. Probably, this discrepancy depends strongly on route of administration and the susceptibility with respect to animals species. Certainly, such data will contribute when using this experimental test-system for understanding oral cancer pathogenesis.